The present invention relates to a connection of a double walled turbocharger housing made of sheet metal with an inner sheet metal shell which conducts hot-exhaust gases and a cold outer sheet metal shell which is spaced apart from the inner sheet metal shell to a flange with a circumferential collar via a common welding seam.
The following discussion of related art is provided to assist the reader in understanding the advantages of the invention, and is not to be construed as an admission that this related art is prior art to this invention.
A connection of the generic type is known from DE 100 22 052 A1. This printed publication discloses in particular in FIG. 5 a double walled turbocharger housing with an impeller housing made of sheet metal, which is surrounded by an outer housing made of sheet metal, wherein between the two housings an air gap is formed. This air gap acts heat insulating and reduces heat radiation. The outer housing is on one side welded to the outlet pipe and on the other side to the connecting flange to the bearing housing. The connecting flange to the bearing housing has on its side which faces the hot exhaust gas a circumferential collar which serves as a stop or counter holder for the outer housing and the inner housing. Although not explicitly described, the inner shell, outer shell and flange are presumably welded to each other via a common welding seam. However, the entire welding seam is exposed to the stress from the hot exhaust gases because at least portions of the welding seam are located in the interior of the impeller housing. During operation, especially the impeller housing is exposed to high thermal stresses i.e., temperature gradients of more than 800° C. The relatively brittle welding seam is not capable to withstand the stresses during continuous operation. In addition, welding spatter in the impeller housing can destroy the turbocharger which necessitates an extremely thorough post processing of the impeller housing.
From DE 102 23 838 C1 an arrangement for conducting exhaust gases of an internal combustion engine is known with at least one flange attached to an end side of a hollow structure, wherein the hollow structure has an outer sheath and an inner sheath. The inner sheath is guided out of the outer sheath on the side of the flange and embraces the outer circumference of an end section of the outer sheath with an outwardly oriented flanged border. The flanged border together with the end section of the outer sheath is inserted into the flange and materially connected to the flange on the side of the flange which faces away from the mouth of the hollow structure. The outer sheath is conically tapered in the direction of the hollow structure in a transitional section. Adjoining the transitional section is an end section of the outer sheath which end section has a tapered diameter and is dimensioned so that it contacts the inner sheath on its outer circumference. After positioning of the hollow structure in the collar of the flange, and in particular after orienting the front surface of the flanged border in the radial plane RE of the collar, the hollow structure is welded to the flange by generating a circumferential fillet weld on the outer circumference of the outer sheath in the transitional region between the transitional section and the end section as well as the radial plane RE of the collar. The flanged border which is framed between the collar and the end section is fixed in a materially bonding manner. In this configuration, the inner sheath and the outer sheath are materially connected with the flange in one step without necessitating post processing due to welding spatter in the mouth region of the hollow structure. A connection of the double walled turbocharger housing in question here is not possible however, because the inner sheet metal shell which conducts hot exhaust gases would jam as a result of contact with the relatively cold outer sheet metal shell during operation due to the heat expansion and as a result would permanently shear off.
DE 10 2009 042 260 A1 shows a turbocharger housing of an exhaust gas turbocharger. The turbine housing includes an outer housing which is welded to a bearing flange. The outer housing delimits a gas tight inner chamber. Located inside the outer housing is an impeller housing which is formed from two sheet metal shells which are welded to each other on the outer circumference of the impeller housing. The outer housing also consists of two sheet metal shells which are also welded together on the outer circumference. The sheet metal shells of the outer housing and the impeller housing which face the bearing flange are connected to the bearing flange. The sheet metal shell of the outer housing is welded via a welding seam to a web which protrudes in radial direction over a base body of the bearing flange. Located upstream of the web in the direction of the impeller housing is a groove which in turn is adjoined by a collar against the front side of which, i.e., in axial direction, the sheet metal shell rests. The sheet metal shell of the impeller housing rests radially outwardly against a projection which protrudes in axial direction. The impeller housing is fixed to the bearing flange at a distance to the outer housing. The distance is selected to be maximal. In addition, the region of contact between the impeller housing and the base body is relatively great. This allows the thermally significantly higher stressed impeller housing to dissipate a correspondingly great amount of heat to the base body. The fixing of the impeller housing on the base body can be materially bonding, form fitting or force fitting. The outer housing and the inner housing are however, connected with the flange separate from one another.
Another connection variant is shown in DE 10 2008 052 552 A1. E19. A turbine housing includes an outer housing which extends from a housing flange up to an outlet flange. The outer housing is welded to the housing flange as well as to the outlet flange and delimits a gas-tight inner chamber. Located inside this outer housing is an impeller housing which is formed by two sheet metal shells which are welded together on the outer circumference of the impeller housing. In this case, only the outer housing is welded to the housing flange. The impeller housing rests on the outer housing and can shift on this support surface. As a result, the impeller housing is not gas-tight.
It would therefore be desirable and advantageous to improve a connection of a double-walled turbocharger housing of the generic type, having improved durability with regard to thermal stresses on the welding seam.